Rotate Camera Around Player Key PresS

Hi all. New to the Unity community :D Recently got Unity3D and have been playing around with it for a bit. Been making a game now for about 3 weeks and all is going well. I have run into a slight problem though.

I have a camera follow script for my player (Who is a ball that rolls when WASD keys are pressed) but I would like to be able to rotate the camera around my player in maybe 90 degree increments when the left or right arrow keys are pressed. I have been trying to get this to work for days. Tried modifying the mouse orbit script but with no success. Also tried searching through the forums but couldn't find anything (May be my poor searching skills but I did look for a while )

I was wondering if anybody could give me any tips on how this could be achieved or if they are being super generous even give me a rough example script. Any help would be greatly appreciated!

(PS: Don't think I am asking for you to write the full script for me as that would be just plain lazy on my behalf but any help would be great :D )